Polyolefin multilayer pipes wherein at least one of the layers of the multilayer pipe comprises a propylene polymer are known.
WO 98/43806 discloses a multilayer plastic tube, comprising a base tube consisting of a propylene polymer, a barrier layer coating the base tube, and a protective layer, containing a lubricant, applied on top of the barrier layer.
WO 97/33117 discloses a multilayer pipe with at least two layers of different plastic materials, in which one layer consists of a Ziegler-Natta propylene copolymer, optionally with 1-30% by weight elastomer content.
The disadvantage of these multilayer pipes is the insufficient balance of high stiffness and good impact properties, especially at low temperatures.